I think most folks who attend gaming conventions like to pick up some souvenir to show that they've been there, done that. Like most, I have a pretty wide selection of con t-shirts, but I'm not too keen on packing them and wearing them at other conventions. For some reason, wearing a Gencon shirt at Origins just feels "off" to me. I also have several caps with convention logos on them I've picked up. (I may pack one to wear, but that's just my penchant for caps.)
But I'd like to share my favorite "gaming con passport" that I have with me at every convention I attend. I have a "neck wallet" that I use to hold my convention ID. (I'm sure many of you have something similar.) I got my first one at Gencon years ago, but this is the one I currently use. I recently had a custom lanyard made using the dungeon map cloth I designed. Well, tucked inside the wallet is my collection of con badges from all other conventions I've attended. The day I get home from a gaming con, the newest "been there, done that" ticket gets tucked in amongst the others. It's become a snapshot of sojourns I've taken. So, do you have a way to mark each con you've been to?